Preparation of poly(amino)urea polymers is well known. U.S. Pat. No. 3,892,696 teaches reaction of polyisocyanates with polyamines in the presence of a carbonyl solvent to produce essentially linear polyureas. After replacing the carbonyl solvent with water, the polyurea can be further reacted with crosslinking agents, e.g. epichlorohydrin or formalin, to provide partially crosslinked polymers which are still water soluble or water dispersible. Polyureas have also been described wherein the reaction with the crosslinking agent is carried out in the carbonyl solvent (see U.S. Pat. No. 3,836,493).
In addition to U.S. Pat. No. 3,892,696 other polyurea systems are also known which are based on a mixture of ketamines or aldimines with polyisocyanates. Such mixtures are stable in the absence of moisture and may be applied as coatings to various substrates. Application of moisture causes unblocking of the ketamines or aldimines to yield free primary amines which react with the polyisocyanates to provide a cured, hard polyurea coating. Illustrative of patents describing such systems are Australian Pat. No. 285,476 and Australian application No. 12,091/66. Also relevant are British Pat. Nos. 1,259,574; 1,125,836; 1,073,209 and 1,088,534. Coating compositions formed by reacting urethane prepolymers with polyamines are also described in U.S. Pat. No. 3,475,266.
Another system useful as wet strength agents is the polyamide formed by reacting adipic acid with diethylene triamine followed by reaction with epichlorohydrin and adjustment of pH to about 5.5 to provide a poly(amino) polyamide wherein the amine groups have been converted to the hydrochloride salt. Such products are described in U.S. Pat. No. 2,926,116.